The present invention relates to impact absorbing devices, and in particular to an energy absorbing impact system and method for vehicle bumpers and the like.
Typical automotive bumper systems include three basic components. The first component is a decorative fascia, usually constructed of plastic or the like. The second component is a rigid impact beam, typically constructed of roll formed or stamped steel, which supports the decorative fascia. The third element is an energy absorption unit or assembly that operably connects the impact beam to the frame rails of an associated vehicle. These three components are designed to meet the performance requirements for both low and high speed impacts.
It is beneficial to design the bumper system in such a way that limited damage is transferred to the vehicle frame rails under impact. One guideline provided for this design process is for the bumper system to have a peak loading capability equivalent to around 85 percent of the combined rail capacity. This assures that the energy absorption unit will crush first upon impact before loading is imparted to the frame rails. It is also beneficial that the bumper system be designed so that energy can be absorbed in a controlled and repeatable manner. This allows for consistency in vehicle crash behavior.
Examples of energy absorption units in bumper systems can be found in U.S. Pat. Nos. 5,224,574; 6,231,095 and 6,409,239, which disclose various structures and methods for meeting the energy absorption targets for certain vehicle bumper systems. However, many of such prior devices include certain shortcomings, including inconsistency in deformation and resultant energy absorption, instability in lateral loading, high manufacturing costs, post impact damage visibility, and large profiles unsuitable for compact bumper designs. Also, while some of these prior bumper systems are relatively effective in absorbing the energy associated with a front end collision, they are not equally effective with side hits or collisions of the type having a significant side component, particularly for high speed crashes.
Hence, a need still exists for an energy absorption system that is compact, lightweight, inexpensive to manufacture, has predictable energy absorption characteristics, and incorporates a relatively simple design that can be readily adapted for a wide variety of different bumper applications.